Af'el is the homeworld of the Defel, who dwell in extensive underground cities all over the planet. The planet's gravitational field is larger than most, which is due to the large mass and density of the planet. Af'el also has no ozone layer, which when combined with the ultraviolet supergiant Ka'Dedus, can cause problems for the any lifeforms on the planet. The planet also has a large number of glaciers, volcanoes and caves, leading to its reputation as a harsh and inhospitable planet.

Due to the unique mixture of gases in the atmosphere, visible light is blocked from the surface, while ultraviolet light passes freely. As a result all animals on Af'el, including the sentient Defel, can only see in the ultraviolet light ranges unless they were raised off-world. This causes many of the Defel to use special eye wear when visiting other planets. Most of the fauna on Af'el live in the caves or in the small forested areas. The majority of species are rodents and small mammals, but some birds and lizards have also been spotted.

Because of the dangerous environment, there have been very few expeditions to the planet to gather more information about its history. Till recent times, Defel lore has been the only source of information and has proven to be inaccurate in most cases. Many xenoarchaeologists plan to gather the necessary equipment to prepare themselves for a series of expeditions, hoping to gain an insight into the enigmatic Af'el.